Influence of temperature in the kinetics of the gas-phase reactions of a series of acetates with Cl atoms

Absolute rate coefficients have been measured for the first time as a function of temperature for the gas phase reactions of chlorine atoms with a series of aliphatic acetates: methyl acetate (k1k1), ethyl acetate (k2k2), nn-propyl acetate (k3k3) and n  -butyl acetate (k4k4). The experiments were carried out using the pulsed laser photolysis-resonance fluorescence technique (PLP-RF), over the temperature range 265–383 K. The obtained kinetic data were used to derive the Arrhenius expressions: k1=(9.31±1.02)×10-12exp[-(359±70)/T]; k2=(4.35±0.65)×10-12exp[(342±92)/T]; k3=(2.22±0.20)×10-11exp[(217±58)/T] and k4=(5.41±1.51)×10-11exp[(245±168)/T] (in units of cm3 molecule−1 s−1). The rate constants obtained at room temperature were as follows: methyl acetate, 0.279±0.031; ethyl acetate, 1.37±0.20; nn-propyl acetate, 4.60±0.41 and nn-butyl acetate, 12.3±3.4 (in units 10−11 cm3 molecule−1 s−1). The results are discussed in terms of structure-reactivity relationships and the atmospherics implications are also analyzed.